1. Field of the Invention
The invention relates to a connection device for connecting a cable, especially an optical fiber, to an electrical device, with a housing, a cable gland, and a plug for insertion into the corresponding socket of the electrical device, the housing having a cable passage for insertion and routing of the cable, the plug being held at least partially in the housing, and being connectable to the fibers or cores of the cable which has been inserted into the cable passage.
2. Description of Related Art
Connection devices for connecting a cable to an electrical device, especially to a communications means, for example, a computer, a notebook or a telephone, are known from practice. The cable is easily connected to the electrical device by the cable being connected to a plug and this plug being inserted into a corresponding socket on the electrical device. In order to simplify connection of the cable to the electrical device, it is conventional for at least one end of the cable to be already connected to a plug.
Known connection devices for electrical cable consist on a standard basis of a cable-side, eight-pin plug which is known in practice as a RJ-45 plug or a Western plug and a corresponding device-side connecting socket. The plug is generally connected to the cable in crimp connecting technology, but can also be soldered to it. The plug is generally fixed by means of a catch arm when inserted into the socket, but can also be held by a fastening hook which is present on the socket or on the electrical device or can be screwed to the electrical device by means of screws.
In addition, there are also connection devices for optical cables, i.e., for optical fibers. An optical fiber is an optical component which is suitable for transport of light and which often formed of a host of individual glass fibers or plastic fibers, especially polymer fibers, which are very thin relative to their length and which are combined into bundles; an optical fiber will however also be defined below as one with an individual fiber. The individual glass fibers or plastic fibers are generally surrounded by a plastic jacket. Larger amounts of data can be transmitted in the same time or the same amounts of data in a shorter time than with conventional coaxial cables due to the carrier frequency of the light which is much higher compared to electrical signals. Moreover, for optical fibers, there are no EMC problems. Compared to glass fibers, a polymer fiber has much higher attenuation values and a large diameter, but it is economical and easier to install.
Based on the development of both transmitting and receiving means and also optical fibers, the losses in transmission of signals over optical fibers are being continually reduced. Thus, the use of optical fibers for transmission of signals has increased greatly in recent years. Therefore, there is an increasing demand for connection devices for optical fibers which can be quickly connected and which are easy to handle (fiber-optic plugs).
For the connection hardware of optical fibers, there is a host of standardized plug connections which are not compatible among one another. The most common standard fiber-optic plugs are ST plugs, PC/FC lugs and SC plugs, the latter becoming increasingly popular. The SC plug (IEC 874-19) is a fiber-optic plug which is characterized as a polarized push-pull plug by its small dimensions and high packing density. This plug has a square design and can be used for multimode fibers and monomode fibers. Simplex, duplex and multiple links can be set up with the plug. Due to its structure, the plug is locked and has automatic interlocking with the corresponding socket. To release such a fiber-optic plug from the corresponding socket, it is necessary to pull the plug housing axially away from the socket by a short path of roughly 1 to 2 mm. In this way, the desired relative displacement of the outer plug housing occurs relative to the inner housing which holds the ferrules, by which the mechanical locking between the inner housing of the plug and the corresponding socket is released.
However, the disadvantage here is that the known standard fiber-optic plugs can only be used very conditionally in a rough industrial environment. Therefore, housings have been developed which hold the standard fiber-optic plugs and protect them against mechanical stresses and against dirt and moisture. For this purpose, the known connection device (see, “Phoenix Contact NEUHEITEN Katalog 2004”, page 152) in addition to the housing which holds the actual plug, has especially a cable gland for sealing the cable to be protected. However, the problem in the known connection device is that the desired safe and strong holding of the plug and of the optical fiber to be connected in the housing, especially the fixing of the optical fiber which is necessary for sealing by means of the cable gland, hinders the axial movement capacity of the plug housing which is necessary for unlocking the plug.